Process of making hydrochloric acid.



H. HOWARD.

PROCESS or MAKI G nvonocmomc ACID.

APPLICATION FILED JUNE 25 I914.

' Patented July 13, "1915;

an I l l@@ HENRY HOWARD, OF BROOKLINE, MASSACHUSET'IQ.

PROCESS OF MAKING HYDROCHLORIC ACID.

Application filed June 26, 1914.

H owAiu), a residing at evolved gaseous hydrochloric acid being absorbed by water in a suitable absorption train. I have found that decided economies in the operation are secured by commingling the salt and acid in accurately predetermined proportions before their introduction into the furnace, and continuously feeding the mixture, in the form of a partially decomposed paste, to a suitable mechanical furnace in which it is stirred and calcined to complete the reaction. By proceeding in this way, a, nearly instantaneous reaction is obtained in the furnace, particularly when the salt is in the form of fine powder, and by feeding the paste continuously and uniformly to the furnace at a rate commensurate with its capacity, there is obtained a copious and uniform evolution of hydrochloric acid gas under conditions highly favorable for economic operation.

This procedure has been found materially to increase the capacity of the furnace, as compared with the results obtainable under the prior practice of separately feeding the salt and acid, and also to render it entirely feasible to carry out the whole operation on a single hearth of the Mannheim type; It is necessary, however, under the present process to provide not only for the al'isorption of the gas evolved by the reaction in the furnace, bu t also for the absorption of the lesser quantities of gas evolved from the reaction mixture or paste before its admission to the furnace.

It is essential to the successful operation that the salt and acid should be delivered to the furnace in the form of a mixture of uniform composition, the components of the mixture being in absolutely controlled relative quantities. Under these conditions, and in a. furnace of the type described, the mixture is fed to a hearth which carries a large quantity of highly heated and nearly dry Specification of Letters Patent.

Patented my is, was. Serial No. 847,500.

sulfate (if soda, with the result that the furace charge as a whole does not at any time assume a liquid or pasty condition, and the reaction may be carried to completion in a single step or stage. This uniformity in the composition of the mixture is secured either by. coordinating the feed of the salt and acid to a suitable mixing device in such manner that these feeds vary proportionately in so far as they vary at all, or

by introducing the salt and acid in proper weighed proportions into a suitable mixing device, inwhich they are thoroughly commingledbefore their introduction into the furnace.

A preferred form of apparatus for carrying the process into effect is illustrated in the accompanying drawing, wherein- Figure lis an elevation of the apparatus, partly in section, and Fig. 2 is a transverse vertical section of the acid-feeding device.

In said drawings, '1 represents, diagrammatically, a single-hearth mechanical saltcake furnace of the Mannheim type, which in practice is provided with the usual. stirring means and is constructed for continuous operation. 2 is the salt pan, provided with a rotary feeding mechanism 3, and discharging through the bottom outlet 4 into a conveyor 5 which leads directly to the furnace 1. The gases evolved from the furnace pass through the standard 6 to a suitable absorption train 7. The conveyer 5 is shown as operated by means of a w0rmgear 8. i

In the apparatus illustrated, sulfuric acid n the required proportion to the salt is fed in successive equal portions to theconveyer 5 at a point between the salt pan and the mechanicalfurnace. A suitable mechanism for feeding the acid .in this manner comprises a horizontal cylinder 90f acid-proof ware, revolubly mounted in bearings 10 and slowly rotated by a worm-gear 11, the ar- 'angement being such that the conveyor 5 And the cylinder 9, interconnected through the belt 12, are always driven in synchronism. The cylinder 9 carries at one end a dipping-tube 13 which revolves in a vertical plane in the direction indicated by the arrow in Fig. 2. This tube is closed at its outer end and is provided on its advancing reaches the horizontal position in its movement of rotation, and delivers equal quantities of acid at each revolution, irrespective of the depth of acid in the tank 15, provided only-enough acid be present to fill the cup end of the tube in its lowermost position. The acid is discharged at each revolution into a small receiving vessel 16, whence it is carried by pipe 17 to the conveyer 5.

By operating the dipping-tube in synchronism with the mechanical conveyer for'the salt; and properly proportioning the capacityand rate of revolution of the tube to the capacity of the conveyer, it is practicable to deliver the proper mixture of salt and acid to the furnace under all conditions and at a controllable rate.

The acid-feeding device as above described is claimed in my copending application Serial No. 848,457 filed July 1, 1914. Instead of this particular form of acid feed, I may employ other devices capable of accomplishing a like result.

In the operation of this apparatus, the pan 2 serves as a storage receptacle for the salt and the conveyer mixes the salt and acid to a substantially uniform paste, while the body of fine salt in the pan and in the rear of the conveyer acts as an effective seal to prevent any escape of the gaseous hydrochlorlc acid. The gas set free by the partial decomposition occurring in the conveyer,

passes into the furnace with the partially decomposed mixture, and thence, together with the reaction gases from the furnace, to the absorption train 7 The invention is not restricted to the employment of the particular apparatus illustrated. For example, if desired, I may supply salt and acid in weighed proportionate quantities directly to the pan 2 which in such case should be constructed of a material resistant to hydrochloric acid, properly covered, and piped to the absorption system. Or, if desired, I may introduce into the pan a mixture of sodium chlorid and acid sodium sulfate, the latter in smaller proportion than is required for the decomposition of the sodium chlorid,the required amount of sulfuric acid to complete the decomposition of the salt being either fed'to the mixture on its way to the furnace as above described, or introduced in Weighed portions into the pan.

The apparatus herein described is claimed in my copending application Serial No. 847,499, filed June 26,191 1.

I claim:

1. A process of making hydrochloric acid, which consists in preparing a uniformly compounded mixture containing salt and sulfuric acid in the necessarypredetermined proportions, absorbing theevolved gas, continuously feeding the resulting partially decomposed mixture to a suitable furnace, heating and, stirrlng 1t therein to complete the reaction in a single stage, and absorbing the evolved gases.

2. A process of making hydrochloric acid, which consists in mixing salt and sulfuric acid, coordinating the supply of salt and acid to maintain the necessary predetermined proportions, absorbing the evolved gas, continuously feeding the resulting partially decomposed mixture to a suitable furnace, heating and stirring it therein to complete the reaction, and absorbing the evolved gases.

3. A process of making hydrochloric acid, which consists in continuously conveying salt from a storage receptacle, mixing the predetermined necessary proportion of sulfuric acid with the moving body of salt in a confined space communicating with an absorption system, coordinating the supply of salt and acid to maintain the necessary predetermined pr(".portions, heating and .stirring the mixture to complete the reaction, and absorbing the evolved gases.

4. A process of mal"ng hydrochloric acid.

which consists in continuously conveying M. V. ,OBRIEN, EVERETT E. BRAINARD.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Yatents.

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